Digital three-dimensional manufacturing, also known as digital additive manufacturing, is a process of making a three-dimensional solid object of virtually any shape from a digital data model. Polyjet three-dimensional printing is an additive process in which one or more printheads or ejector heads eject successive layers of material on a substrate in different shapes. The substrate is supported either on a platform that can be moved three dimensionally by operation of actuators operatively connected to the platform, or the printhead or printheads are operatively connected to one or more actuators for controlled movement of the printhead or printheads to produce the layers that form the object. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
Three-dimensional objects produced with these printers can be made of a variety of materials that can be ejected from ejectors of the printhead or printheads onto the substrate. Thus, one issue that arises in the production of three-dimensional objects with a three-dimensional printer is that the material of which the three-dimensional object can be made is limited to that which can be ejected through the ejectors onto the substrate. To be ejected through ejectors, a material must be able to be heated to a non-solid state having a viscosity suitable for ejection as discrete droplets onto the substrate. The precise viscosity and temperature of the material varies depending on the type of ejectors and the geometry of the printheads. However, in general, materials having a high melting temperature or a low freezing temperature are typically unsuitable for production of three-dimensional objects due to the difficulty of maintaining a suitable temperature and viscosity of the material during operation of the three-dimensional printer.
One example of a material having a high melting temperature is polytetrafluoroethylene (PTFE). When it hardens, PTFE provides a smooth surface having a low coefficient of friction. Accordingly, producing three-dimensional objects with smooth areas arising from the presence of PTFE would be advantageous. A three-dimensional object printer capable of producing objects made from materials having a high melting temperature, such as PTFE, or a low freezing temperature would be advantageous because a three-dimensional object printer capable of forming objects with regions having different coefficients of friction would be beneficial.